Assets worth around 10 million euros ($10.8 million) including restaurants, cars and checking accounts were seized as part of the operation, which was code-named "The imitation game", Xinhua quoted newspaper Corriere della Sera.
The illicit businesses were carried out through as many as 12,000 virtual gaming tables throughout Italy.
A businessman in the gaming sector renowned both in Italy and abroad, Luigi Tancredi, was among the people arrested. Tancredi, known as "The king of slots," was the key figure behind the illicit activities, investigators said.
His criminal group had created "a system of gambling and online games much more profitable than drug trafficking," prosecutor Michele Prestipino told a press conference in Rome later on Wednesday.
Investigators found that the server of the group's main illegal website, named "dollaropoker," had been placed in Tampa, United States, while the computer technicians working at the site were located in Romania.
Though not directly belonging to a mafia syndicate, Tancredi allegedly had close links with members of a powerful clan within Camorra, the Naples-based mafia.